The effect of boron substitution on the structure of calcium-aluminosilicate calcium-fluoro-aluminosilicate glasses and glass-ceramics

• Main Author: Zhang, Siqi
• Published: University of Birmingham 2017
• Subjects: 620.1; TJ Mechanical engineering and machinery
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.701856

This work focuses on the effect of boron substitution for aluminium on the structure o£ a series of fluorine-free (4.5Si02-3A12O3-1.5P205-5Ca0) and fluorine-containing (4.5Si02-3A1203-1.5P205-3Ca0-2CaF2) glasses and the resultant glass ceramics has been studied by using a combination of analytical tools like helium pycnometer, FTIR, Raman, XRD, multinuclear MAS-NMR spectroscopy and thermal analysis by DSC and TGA. The morphology of the crystal phases was observed by ESEM, and the identification of the composition observed was achieved by EDX. The density of both boron-substituted aluminium glasses and glass ceramics decreased with increasing boron content. The glass transition temperature decreased generally with an increase of boron substitution in fluorine-free glasses. When the sintering temperature was raised to 1100°C, the calcium phosphate (C'4P20 9) phase transferred to the tricalcium phosphate [Ca3(P04)2] phase, and anorthite and aluminium phosphorus phases were crystallised. The fluorapatite phase was the first phase to be formed in the fluorine-containing glass ceramics, and with the sintering temperature raised to 1100°C, the mullite and aluminium phosphorus phases were crystallised. All the NMR results investigate the structure of boron-substituted glasses and glass-ceramics which are agree with XRD results. ESEM and EDX analysis showed changes in the composition of glass ceramics with boron substitution.